The invention relates to marine drives, and more particularly to a marine drive shift control system.
Marine drives typically have an internal combustion engine driving a propulsor through a transmission shiftable between forward and reverse in clutched engagement with forward and reverse gears, respectively. When the transmission is shifted from forward gear, particularly wide open throttle, to reverse gear, engine speed drops significantly more quickly than vessel over water speed. The latter is directly proportional to the propeller speed when free wheeling in neutral gear. The difference in engine speed (and consequently transmission input speed) and the vessel over water speed (and consequently propeller speed and transmission output speed) causes a high rotational speed difference (e.g. up to 2,000 rpm) in the clutch mechanism of the transmission during entry into reverse gear. The action of closing the reverse clutch under full pressure at these high rotational speed differences can cause engine stalling and increased wear on major driveline components. Current production methods utilize full gear pressure when closing the clutch, regardless of vessel or propeller speeds. Save for troll mode, there is no allowance for slip during clutch engagement. One known solution is the use of speed over ground from a global positioning system antenna to limit entry into reverse gear. Another solution uses engine torque control for a similar goal.
The present invention arose during continuing development efforts in the above technology.